1. Field of the Invention
The present invention relates to a vacuum circuit breaker used in a system to distribute electricity for industry, and particularly, to a vacuum circuit breaker in which a main circuit part and a mechanic part are arranged in a longitudinal direction.
2. Background of the Invention
Generally, a circuit breaker is an electricity protecting apparatus capable of protecting a load device and a line from a large current due to a shortening, a ground accident, etc. that may occur on an electric circuit. When an accident circuit occurs, the circuit breaker opens a circuit by automatically performing a breaking operation.
One type of the circuit breaker, a vacuum circuit breaker is configured to rapidly opens a circuit by extinguishing, in a vacuum container, an arc generated when opening/closing a normal load and when breaking an accident current.
FIGS. 1 and 2 are a perspective view showing one example of a vertical type vacuum circuit breaker in accordance with the conventional art.
As shown, the conventional vertical type vacuum circuit breaker comprises a main circuit part 10 having a fixed contact 12 and a moveable contact 14, and configured to conduct a main circuit and to break an abnormal current; a mechanical part 20 configured to generate an operational force so as to connect the circuit between the two contacts 12 and 14 of the main circuit part 10 to each other, or to disconnect the circuit from each other; a link frame 30 long installed below the mechanical part 20 and the main circuit part 10 in back and forth directions; and a link unit 40 provided in the link frame 30, and configured to convert one rotation motion into a plurality of vertical motions while moving in back and forth directions so as to transfer an operation force of the mechanical part 20 to the moveable contact 14 of the main circuit part 10.
The main circuit part 10 consists of three for R, S and T phases, and is fixedly-installed in a vertical direction above the link frame 30 from a backside of the mechanical part. Each of the main circuit parts 10A, 10B and 10C includes a main circuit housing 11 installed above the link frame 30 in a vertical direction, a fixed contact 12 positioned at an inner upper part of the main circuit housing 11, an insulation rod 13 connected to the link unit 40 and vertically moveable in the main circuit housing 11, and a moveable contact 14 fixed to an upper end of the insulation rod 13 and contacting or separated from the fixed contact 12 while vertically moving.
The link unit 40 includes a rotation shaft 41 provided in the mechanical part 20, a rotation link 42 configured to convert a rotation motion of the rotation shaft 41 into a motion force in back and forth directions, a moveable link 43 having a fore end rotatably connected to the rotation link 42 and movable in back and forth directions by being long connected to inside of the link frame 30, and three direction conversion links 44 sequentially connected to the three main circuit parts 10 above the moveable link 43, and configured to convert motion in back and forth directions into a vertical motion.
The moveable link 43 includes a sliding lever 45 implemented as two long bars are fixed with a predetermined gap therebetween, and a guide link disposed between the two bars of the sliding lever 45, configured to transfer a horizontal motion force of the sliding lever 45 to the direction conversion links 44, and configured to provide a suitable compression force to the direction conversion links 44.
The guide link 46 includes a guide rod 47 having both ends rotatably connected to the sliding lever 43 and the direction conversion links 44, and capable of performing a relative motion in back and forth direction with respect to the direction conversion links 44, and a contact pressing spring 48 supported by the guide rod 47 and configured to provide an elastic force in a direction to perform a relative motion with respect to the direction conversion links 44.
Unexplained reference numeral 49 denotes a connection lever of a rotation link.
The operation of the conventional vertical type vacuum circuit breaker will be explained as follows.
Once the rotation shaft 41 rotates by an operation of the mechanical part 20, the rotation link 42 coupled to the rotation shaft 41 rotates, and the moveable link 43 moves to a rear side, i.e., to a direction far from the rotation shaft 41. As a result, the three direction conversion links 44 simultaneously rotate.
As upper parts of the direction conversion links 44 rotate, each insulation rod 13 vertically moves upwardly in the main circuit part 10 to push up the moveable contact 14 thereby to contact the moveable contact 14 to the fixed contact 12. Accordingly, an operation force of the mechanical part 20 is transferred to the main circuit part 10 to allow a main circuit to be closed.
When the movable link 43 transfers the motion force received from the mechanical part 20 in back and forth directions, the same force and speed are provided to each direction conversion link 44 connected to the link frame 30 with the same interval. This may allow the moveable contact 14 and the fixed contact 12 inside each main circuit part 10A, 10B and 10C to contact each other with the same force.
If the rotation shaft 41 continues to rotate by an operational force of the mechanical part 20 even in a state that the moveable contact 14 and the fixed contact 12 come in contact with each other, the moveable link 43 also continues to move backwardly. Then, the moveable link 43 compresses the contact pressing spring 48, and the guide rod 47 rotates the moveable link 43 in a state that the contact pressing spring 48 maintains an elastic force. Accordingly, the insulation rod 13 is upwardly moved. As the moveable contact 14 and the fixed contact 12 have a suitable contact force therebetween by the elastic force provided to the direction conversion links 44 from the contact pressing spring 48, a closing operation of the mechanical part 20 is completed.
However, the conventional vertical type vacuum circuit breaker may have the following problems.
Firstly, a driving force of the mechanical part 20 is transferred to the contact pressing spring 48 via the rotation link 42 and the moveable link 43, thereby compressing the contact pressing spring 48 and allowing the moveable contact 14 to contact the fixed contact 12 by the compression force. Accordingly, the moveable link 43 receives a compression stress by a compression amount of the contact pressing spring 48 thus to be buckled. This may change a contact motion distance and a contact pressure when compared with initial design values of the vacuum circuit breaker. As a result, the vacuum circuit breaker may have a lowered reliability.